This invention relates to an amide group-containing diisocyanate compound, a process for producing the same, an amide group-containing epoxy resin, and a process for producing the same.
It has been known that since polyamide resins have amide bonds wherein nitrogen atom and a carbon atom are bound with high polarity, a strong hydrogen bond and a large bond energy, these resins are excellent in heat resistance but low in solubility in organic solvents. For example, almost polyamide resins dissolved in only special high boiling-point polar solvents having a large dissolving power such as N-methyl-2-pyrrodidone. Thus, when such resins were used as coating resins and subjected to low-temperature baking wherein heat treatment such as drying, curing, and the like were carried out below the boiling point of such high boiling-point solvents, since the solvents were retained in the coating film after baking, not only coating film properties of the polyamide resins originally had were not exhibited sufficiently, but also various undesirable influences due to the retained solvent were generated. Therefore, such polyamides were only used for high-temperature baking wherein the high boiling-point solvents were completely vaporized and flown away.
Recently, in order to solve such a problem, there have been developed and commercially available copolymer-based aliphatic polyamides soluble in lower alcohols having low boiling points, and aliphatic polyamides wherein whole or a part of hydrogen atoms in amide bonds are substituted with alkoxymethyl groups, ethylol groups, etc. Since these polyamides have active amino groups and imino groups in the molecule, they are well used as a curing agent for epoxy resins for coating due to being able to impart properties such as heat resistance, moisture resistance and flexibility inherent to polyamides to epoxy resin cured articles. But since the amino group and imino group are highly reactive with the epoxy group and easily proceed a curing reaction even at room temperature, the pot life (a usable period) is very short even if used as a two-pack type coating composition. Even if the amino group and imino group are neutralized with various acids to form salts which have latent curing properties, it is impossible to obtain a sufficient pot life.
On the other hand, polyamide resins, polyurethane resins and polyurea resins having amide groups in the molecules have a large agglomerating energy due to high polarity of the amide group and the strong hydrogen bond. Particularly the polyamide resins have widely been used as a curing agent or an additive for epoxy resins, since they can provide higher adhesiveness to epoxy resin cured articles due to the large agglomerating energy. But generally speaking, compatibility of polyamide resins with epoxy resins is poor, so that uniform cured articles are not always obtained when the two resins are mixed, and qualities such as adhesive reliability are not always sufficient.